ARM: omap2plus: remove irq-related global base addresses

After the MULTI_IRQ_HANDLER conversion, a couple of global
variables can be removed.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Conflicts:
	arch/arm/mach-omap2/include/mach/omap4-common.h
	arch/arm/mach-omap2/io.c
	arch/arm/mach-omap2/omap4-common.c
	arch/arm/plat-omap/include/plat/irqs.h